This invention relates to a novel vacuum/hydraulic control system, and more particularly to a control system for synchronizing the speeds of a pair of shafts through control of the extension of brake cables commonly associates with motor vehicles.
Many times operators of motor vehicles find themselves in the annoying predicament of being stuck in a snowdrift, muddy road, or the like, where one drive wheel is resting on such a slippery spot that the coefficient of friction is too low to provide traction, with the result that the wheel spins, dissipating all the driving power of the engine, and the vehicle stands still. The characteristics of differentials in general use on motor vehicles are such that the wheel with no traction spins, and the wheel that has a good coefficient of friction with the road receives no torque.
Any number of methods and devices have been used to reduce the speed of the spinning wheel so that the wheel that has good traction receives torque, enabling the vehicle to move out of its stuck condition. U.S. Pat. No. 1,682,781 discloses such a control system. However, as can be seen in U.S. Pat. No. 1,682,781, the control system operates through a fluid hydraulic arrangement connected directly to the wheel brake mechanism. U.S Pat. No. 1,918,465 also discloses a control system which is adapted for use with the standard hydraulic braking systems in which the brake pedal operates a hydraulic pump from which conduits extend to the individual brakes.
An alternative method of obtaining individual brake control is seen in U.S. Pat. No. 2,466,837. Again, the invention disclosed in U.S. Pat. No. 2,466,837 utilizes a system which operates with a fluid under pressure and further includes conduits for the transfer of the fluid to the wheel brakes. With the aid of a distributing and cut-off valve connected to the brake master cylinder, from which valve the wheel brake conduits extend and through which under the appropriate operating conditions all wheel brakes except that of the spinning wheel are cut off from the braking fluid, depression of the brake pedal results in individual braking of the spinning wheel. Likewise, U.S. Pat. No. 2,346,175 discloses a control system providing valves in the fluid pressure lines to permit blocking the transmission of fluid pressure to those lines which connect the pedal cylinder with the brakes of the non-spinning wheels. In U.S. Pat. No. 2,583,307 a hydraulic control system is shown which synchronizes the speed of a pair of shafts, particularly those found in the rear axle of an automobile or truck. By using gear type, positive displacement pumps driven by the axle, in combination with pressure by-pass valving, the speed of the faster spinning wheel can be reduced.
None of the devices disclosed or known to the inventor operate on the vehicle's emergency braking system. All previous inventions are directly or indirectly linked to the vehicle's standard fluid hydraulic braking system. The obvious problems associated with such devices include modification of the hydraulic brake system with increased risks of leakage and interference with normal braking operation.